In image display apparatuses using a fluorescent substance, for example, cathode-ray tube display devices (CRTs), plasma displays (PDPs), vacuum fluorescent displays, and field emission-type displays, for example, an electron beam or ultraviolet light is applied to the fluorescent substance to cause fluorescent emission of the fluorescent substance, and an image is displayed by taking advantage of transmitted light or reflected light from the fluorescent screen.
For image display devices using a fluorescent substance, it has been often pointed out that, due to high reflectance of the fluorescent substance, reflection of external light from the surface of the display device occurs resulting in lowered visibility of displayed images. In order to prevent the external light reflection and thus to improve the visibility, an optical laminate formed of an anti-dazzling laminate or an antireflective laminate has hitherto been used on the surface of the image display apparatus.
However, it has been often pointed out that, since the fluorescent substance in the image display device is white, the reflectance is so high that external light-derived reflected light is likely to occur and, further, reflected light often occurs as scattered light within the optical laminate and the fluorescent substance in the image display device and, as a result, these reflected light and scattered light affect luminescent color from the fluorescent substance, making it impossible to provide images possessing excellent contrast (particularly black reproduction) and light transmission.
In order to suppress this phenomenon, Japanese Patent Laid-Open No. 26704/1998 proposes an optical laminate comprising a colored material (layer) provided between the surface of a display device and an antireflective laminate. Since, however, the colored material (layer) per se has low transmittance, the total light transmittance is disadvantageously lowered to about 50 to 70% and, consequently, image reproduction is often lowered. Further, Japanese Patent Laid-Open No. 167118/2003 proposes a structure comprising a filter for an electronic display device, coated with a chemical substance having very small transmittance to a specific wavelength without providing any colored material (layer) or any pressure-sensitive adhesive layer.
However, urgent development of an optical laminate which can effectively prevent external light reflection, has a high level of total light transmittance, and, at the same time, can realize images having excellent contrast are still demanded.